<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <input type="button" name="" id="" value="这是一个按钮">
</body>
<script>
    let button = document.querySelector("input")
    button.onclick = function(){
        alert("hello")
    }
</script>
</html>